Apparatus for controlling the flow of molten metal



April 9, 1963 W. O. STAUFFER ETAL APPARATUS FOR CONTROLLING THE FLOW 0F MOLTEN METAL Filed April 23, 1958 3 Sheets-Sheet 1 23 24 as as 'd/J h f A9 2/ 353w 4 20 x /5 66 a 2 2 /2 2 r /4 ,3 /a 6 7 (r R 6 777) 9a 25 23 24 V a3 a4 9 {a 5 INVENTORS.

WILL/AM a STAUFFER 7 BY JAMES E DORE A TTOPNE V April 9, 1963 w. o. STAUFFER ETAL 3,084,925

APPARATUS FOR CONTROLLING THE FLOW OF MOLTEN METAL Filed April 25, 1958 3 Sheets-Sheet 2 INVENTORS. W/LL/AM O. STAUFFER JAMES E. DORE BY 5 fa ATTORNEY April 9, 1963 w. o. STAUFFER ETAL 3,084,925

APPARATUS FOR CONTROLLING THE FLOW OF MOLTEN METAL Filed April 23, 1958 3 Sheets-Sheet 3 mvllllllllm INVENTORS.

WILL/AM O SMUFFER JAMES E DORE ATTORNEY United States Patent and James E. Aluminum 8; a corporation This invention relates to the handling and control of molten metal. More particularly this invention relates to a method and apparatus for releasing, controlling and stopping the flow of molten metal from a source thereof, e.g., a furnace or other molten metal receptacle.

In the casting of metal, e.g., aluminum and aluminum alloys, it is common practice to provide a body of molten metal in a suitable holding receptacle, e.g., an open hearth or reverberatory furnace, electrical resistance heated fur nace or induction heated furnace. The open hearth fur nace, which may be oil, gas, coal or coke fired, is cornmonly used for supplying molten metal for casting and may comprise a melting hearth and a holding hearth. In preparing the metal for casting the charge of metal and any desired alloying constituents to be melted are generally added in the melting hearth and thereafter the molten metal is transferred to the holding hearth where it is subjected to cleaning treatment and where control may be had of the composition and temperature of the molten bath. The treated molten metal may then be transferred from the holding hearth to the casting station by suitable means, e.g. a transfer trough. In handling the molten metal as above described it is necessary to provide means for releasing, controlling and stopping flow of molten metal from the holding hearth to the trough, casting station or ladle.

According to prior art practice releasing, controlling and stopping the flow of molten metal is accomplished by inserting a conical plug of a suitable molten metal resistant material, known in the art as a check-rod tip, in the molten metal outlet. It is customary to coat the conical plug with material such as a mixture comprising a suitable fiber material, such as asbestos shorts, flour and water. This material is known in the art as dough and the operation of sealing the tap hole by such means is referred to as doughballing. This dough" performs two functions. First, it fills any discontinuities in the outlet thus providing a tight seal and second, the carbonization of the flour provides a bond which although weak, prevents the metal head in the furnace from forcing the plug out of the orifice.

Such practice possesses many inherent disadvantages, particularly with regard to casting aluminum where it is desired to produce high quality metal with a minimum of porosity and inclusions. As mentioned hereinabove, the bond formed by the carbonization of the flour is quite weak. This makes it difficult to obtain a leak proof seal when doughballing against relatively high metal heads, particularly with large tap holes. The trend in present day practice is to employ higher and higher heads in molten metal receptacles. When employing doughballing the maximum head which may be employed is very limited. With such practice high heads result in leaky seals which may cause hazards to safety, production delays and damage to casting equipment. Even in the plastic stage the doughball material possesses very little strength. This makes closures of the tap hole difficult at high metal velocities because of the washing action of the metal.

Further, when a furnace is tapped a portion of the doughball remains in the outlet. If this material is not removed regularly, buildup in the outlet occurs thereby restricting the metal flow from the outlet. The doughball" material contains water, inert filler material and carbonaceous matter which latter represents a potential source for gassing the metal resulting in porosity in the ultimate cast body. The doughball material is quite friable and breaks up into pieces when the furnace is tapped. These fragments represent a potential source of non-metallic inclusions.

In addition, when tapping a furnace employing the methods and apparatus of the prior art turbulence and cascading generally occur in the tap hole area which results in regassing and entrapment of oxide films in the metal. These conditions alfect the quality of the ingot being cast. Further. conventional doughballing methods result in solidification of metal and metallic oxides at the entrance to the tap hole. As a result, tapping or starting metal fiow frequently requires the use of an oxygen lance to open the tap hole area. The use of an oxygen lance delays the casting operation and results in damage to the tapping block. Also, the apparatus of the prior art merely provides means for releasing and stopping metal flow and fails to provide means for controlling the rate of flow of molten metal. In addition, doughballing operations require an excessive amount of labor.

Accordingly, the primary purpose and object of this invention is to provide an improved method and apparatus for releasing, controlling and stopping flow of molten metal from molten metal receptacles which eliminates or substantially reduces many of the disadvantages of the prior art techniques.

Another object of this invention is to provide a novel method and apparatus for releasing, controlling and stop ping fiow of molten aluminum metal from a receptacle for molten aluminum wherein such defects as porosity and inclusions may be eliminated or substantially reduced in the ultimate cast body.

Another object of this invention is to provide a novel method and apparatus for releasing, controlling and stopping molten metal flow from a molten metal receptacle whereby the problem of buildup of material in the outlet is eliminated or substantially reduced and adequate metal delivery is assured. 1

Another object of this invention is to provide a novel apparatus for use in conjunction with the transfer of molten metal from a molten metal receptacle whereby the molten metal flow may not only be released and stopped but the rate of flow may be controlled.

Another object of this invention is to provide a novel apparatus for releasing, controlling, and stopping molten metal flow from a molten metal receptacle with a minimum expenditure of labor.

Another object of this invention is to provide a novel apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal receptacle including a tapping block provided with an orifice. a plug adapted to be disposed at least partially Within said orifice having a spherical segment seating surface whereby a line of contact may be made between said spherical segment seating surface and the inner periphery of said orifice when said spherical segment contacts said orifice.

In accordance with this invention, releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle is accomplished by the combination of a tapping block provided with an orifice for the pars sage of the molten metal, a flow channel on the outlet side of said orifice and a plug of novel configuration adapted to be disposed at least partially within said orifice.

The orifice embodying the principles of this invention has a rounded inlet edge and a rounded outlet edge, the radius of curvature of said outlet edge being relatively small. The orifice is inclined at an angle to the horizontal with the outlet end at a higher position than the inlet end. The lower surface of the flow channel has a downward pitch away from the orifice while the upper surface has an upward pitch away from the orifice. It is preferred that the upper surface have a curvature such that a transverse cross section defines a segment of a circle, eg. a cylindrical segment surface or a conical segment surface. The center line of such curvature preferably is parallel to the center line of said orifice.

The plug configuration is characterized by a spherical segment seating surface whereby a line of contact may be made between the spherical segment seating surface and the outlet edge of the orifice and an elongated end portion extending from the spherical segment surface into the orifice. This elongated portion is adapted to control the rate of flow of molten metal passing through the orifice whereby the rate of flow increases as the plug is withdrawn from the orifice.

Suitable means are provided for moving the plug into and out of the orifice and for maintaining the plug in tight contact with the orifice. This actuating mechanism is provided with counterweight means whereby the end of the plug when withdrawn from the orifice is maintained against the upper surface of the flow channel. Since the upper surface of the flow channel preferably takes the form of a cylindrical segment or a conical segment it guides the plug into the orifice as the plug is moved toward the orifice. The angle of inclination of the center line of the orifice and of the center line of the curvature of the upper surface of the flow channel is such that the plug may be moved in a straight line into and out of the orifice.

For purposes of more detailed discussion, this invention will be specifically described with reference to the embodiment shown in the accompanying drawings wherein:

FIGURE 1 is an elevational view in cross section, with parts removed for purposes of clarity, of a portion of a molten metal receptacle illustrating the novel tapping block, plug and actuating mechanism of this invention.

FIGURE 2 illustrates a second embodiment of the plug and control rod of this invention wherein the plug is segmented.

FIGURE 3 is an elevational view in cross-section with parts removed for purposes of clarity, of a portion of a molten metal receptacle, tapping block, plug and actuating mechanism of this invention illustrating a second embodiment of the tapping block of this invention wherein the tapping block is segmented.

FIGURE 4 is an elevational view partially in crosssection, with parts removed for purposes of clarity, of the molten metal receptacle of FIGURE 1 illustrating an automatic control means for controlling the position of the plug during tapping of the molten metal.

FIGURE 5 is an elevational view of the molten metal receptacle and automatic control means of FIGURE 2 taken along a plane transvense to that of FIGURE 2.

FIGURE 6 is an electrical and pneumatic diagram of the control means of FIGURES 4 and 5.

Referring now more particularly to the drawings in which the same reference numerals have been applied to various corresponding parts and with particular reference to FIGURE 1, the present invention involves the use of a tapping block 1 provided with a tap hole or orifice 2 and a plug 3. A molten metal body 4 is contained in a suitable holding receptacle 5.

The edge 6 of the inlet end of the orifice 2 is rounded off thereby eliminating stagnant flow areas and reducing accumulation of dross and other materials at the orifice 2 while casting. It is preferred that the ratio of the radius of curvature of the edge 6 to the minimum inside diameter of the orifice 2 range from 0.25 to 1.0. Further it is preferred that the minimum inside diameter of orifice 2 should be not greater than 4 /2 inches. It has been found that the minimum diameter whereby plugging would be avoided is of an inch. In order to avoid chipping of the outlet edge 7 of orifice 2, edge 7 should be either chamfered or rounded. For best contact with plug 3 it is preferred that edge 7 be rounded with a radius of curvature ranging from 0.125 to 0.475 inch and an arc length ranging from 30 to With the exception of the rounded inlet edge 6 and the rounded or chamfered outlet edge 7, the inside surface of orifice 2 may be any of several contours. The most simple surface is a hollow cylinder of uniform inside diameter. However, the inside surface may also be formed to the contour of one or two frustrums of right circular cones, one or two segments of circular parabolic or free curved tori, and any combination thereof including combinations with or without a right circular cylinder. A preferred inside surface is the one illustrated in FIGURES 1 and 2 which is made up of a segment of a torus, and two right circular cones. The orifice 2 is inclined whereby the center line is at an angle to the horizontal ranging from 10 to 60, preferably from 20 to 45, with the outlet end at a higher position than the inlet end.

The internal configuration of the tapping block should be such that a flow channel 11 is defined therein on the outlet side of orifice 2. The lower surface 76 of flow channel 11 should have a downward pitch away from the orifice 2 ranging from about 10 and 30 to the horizontal to allow the metal to drain away from the orifice 2. A pitch less than 10 would not provide sufficient drainage to prevent buildup around orifice 2 while a pitch greater than 30 would result in excessive turbulence which tends to result in oxide inclusions and regassing of the metal. The upper surface 12 of the flow channel 11 has an upward pitch away from orifice 2, and takes the form of either a segment of a cylinder or a segment of a cone. As will be described in greater detail hereinafter, by maintaining the end of plug 3 in contact with the upper surface 12, the upper surface will serve as a guide whereby plug 3 may be guided into orifice 2.

The center line of the segment of a cylinder or cone forming upper surface 12 is parallel to the center line of orifice 2. By having the center lines of the orifice 2 and the upper surface of the flow channel 11 at an angle to the horizontal, a straight line valving action for inserting and withdrawing plug 3 is made possible wherein the actuating mechanism is out of the molten metal and line of contact seating is permitted. It has been found preferable that the length of the tapping block 1 should range from 1.1 to 1.5 times the thickness of the refractory wall 10 of holding receptacle 5 in which the tapping block is placed. This eliminates the need of a short transfer trough which is employed in conventional metal transfer equipment and the problems encountered in the use of a short transfer trough such as expansion cracks and a friable unfired refractory lining. The configurations of the outlet of flow channel 11 may take the shape of the internal contour of a transfer trough where a transfer trough 66 is employed, as in most conventional transfer operations.

Plug 3 has a compound configuration whereby said plug is adapted for both closing orifice 2 and controlling the flow of molten metal when plug 3 is withdrawn from orifice 2. This compound configuration comprises a spherical segment seating surface 14, whereby a line of contact may be made between seating surface 14 and the outlet edge 7 of orifice 2, and an elongated end portion 13 extending from surface 14 into orifice 2 when surface 14 contacts edge 7. The elongated end portion 13 of the plug has a shape substantially conical or other shape suitable for controlling metal flow by movement of said plug into 01' out of orifice 2. While a frustrum of a cone having a rounded end is shown in FIGURE 1, the surface of end portion 13 could be curved. It is preferred that the radius of curvature of the seating surface 14 range from 0.6 to 1.2 times the exit diameter of the orifice. When the curvature of seating surface 14 is spherical a line of contact seal in the form of a true circle is obtained regardless of small differences in angularity between the center line of plug 3 and the center line of orifice 2. If seating surface 14 had any curvature other than spherical perfect straight line valving action would be essential requiring expensive valving mechanisms of great precision.

The phrase, line of contact seating as used herein may be defined by reference to FIGURE 1. From FIG- URE 1 it can been seen that the spherical segment seating surface 14 of plug 3 contacts the rounded outlet edge 7 at two points in the plane shown in FIGURE 1. By rotating this plane 180 about the center line of the orifice 2, the locus of the points of contact would generate a circular line. This circular line is the line of contact as used herein. Line of contact seating has many advantages over the plane of contact seating employed in the prior art, i.e. contact over a zone of appreciable breadth rather than a line. For example, fouling of the seating surface on the valve plug and/or tap hole is minimized. A particle or obstruction must lodge along the line of contact to prevent mating and closure of the valve. Positive seating action is obtained and the seating areas on the valve plug and orifice insert are self-cleaning in nature. All of the force applied to the valve plug during the seating operation is concentrated at the line of contact between the valve plug and the orifice insert. Since this contact area is very small (e.g., a line several thousandths of an inch wide), the load per unit area is extremely high and this generally dislodges or removes any obstruction of a non-metallic nature which has fouled the seat.

It has been found that for the direct valving action of this invention it is desirable to have a wet or mushy seal at the line of contact between the seating surface 14 of plug 3 and the orifice 2. If a small amount of metal were permitted to freeze at this line of contact, withdrawal of the plug from the orifice would be difficult and damage to the edge 7 of the orifice 2 may result. Damage to the edge 7 would make sealing of orifice 2 with plug 3 impossible. Accordingly, the materials of construction for the plug 3 and the material surrounding the orifice 2 should have high thermal conductivity such that the heat from the body of molten metal 4 is conducted to the line of contact between edge 7 and surface 14 whereby freezing is prevented. Further, the shape of plug 3 is such that the molten metal at the line of contact is sufficiently thick to avoid easy freezing. Other important properties for the material surrounding orifice 2 and the plug 3 are abrasion resistance, metal attack resistance, hardness and good thermal shock resistance. The principal material prerequisites for the main portion of tappink block 1 are high strength, thermal shock resistance, abrmion resistance and a relatively low thermal conductivity as compared to that of the material immediately surrounding the orifice 2. Accordingly, it is preferred that the orifice 2 be provided in an insert 8 of a different material than that of the body 9 of tapping block 1.

In order to facilitate insertion and removal of insert 8 and to avoid undue stresses due to differential expansion, a layer of resilient refractory material 77 may be provided between insert 8 and tapping block body 9. Examples of refractory materials that are suitable for the body 9 of the tapping block 1 include a 90% alumina composition, mullite, stabilized zirconia, magnesiumaluminate spine], zircon and combinations thereof. Pre fe'rred materials of construction for the valve plug 3 and the insert 8 include silicon-nitride, silicon-nitride bonded silicon carbide, pure silicon carbide (self bonded or re crystalized silicon carbide) and the refractory hard metal borides, carbides and nitrides of metals such as titanium, zirconium, chromium, etc. or mixtures thereof.

Suitable means are provided for moving plug 3 into and out of orifice 2 and for maintaining plug 3 in tight contact with orifice 2. One such means is shown in FIGURE 1 and comprises a control rod 15 on which plug 3 is mounted by means of a sleeve 16 of a suitable 6 Sleeve 16 is affixed by suitable means, such as welding, to a collar 17 which in turn is welded to control rod 15. Sleeve 16 has an internal diameter slightly larger than the outside diameter of plug 3 whereby it may fit over the end of plug 3 opposite the end portion 13. Plug 3 is affixed within sleeve 16 by means of a pin 18 passing through openings 19 in sleeve 16 and a matching opening 20 in the end of plug 3. Since the refractory material of which plug 3 is fabricated is generally somewhat brittle, a suitable resilient refractory material 21 is provided between the end of plug 3 and collar 17 to avoid undue physical stress being imparted to plug 3 by the valve actuating mechanism. It has been found that aluminum silicate fiber materials are suitable for the resilient refractory material 21. By the term aluminum silicate fiber materials is meant materials obtained by melting and fiberizing mixtures of alumina and silicon with or without modifying agents such as borax, glass, zirconium, and soda ash. One example of an available commercial material of this type suitable for this application comprises 51.2% A1 0 47.5% SiO 0.6% B 0 0.6% Na O. balance MgO, CaO. F6203 and impurities in minor amounts. Control rod 15 is pivotally suspended from a pair of hook members 22 by means of a shaft 28 affixed to a cylinder 29 by suitable means such as welding.

In order to prevent accidental dislodging of shaft 28 from hooks 22 when plug 3 is in contact with edge 7 of orifice 2 to prevent fiow through orifice 2, hooks 22 are fabricated as shown in FIGURES 1, 3 and 4 whereby the end portions 96 overlap the upper surface of shaft 28. Thus shaft 28 cannot be forced upwardly out of hooks 22 unless books 22 are rotated about shaft 23 a sufiicicnt amount to release the pressure imparted by hooks 22 on shaft 28 whereby shaft 28 may be moved to the left and then upwardly out of hooks 22. Cylinder 29 has an interior cylindrical surface of a diameter larger than the diameter of control rod 15. At the end of cylinder 29 furthest removed from shaft 28 a plate 30 is afiixed by suitable means such as welding. Plate 30 has a threaded opening 31, the center line of which coincides with the center line of cylinder 29 and is adapted to engage suitable threads 32 on the end of control rod 15.

The end of control rod 15 opposite the end affixed to plug 3 is provided with a handle 33 whereby control rod 15 may be moved longitudinally through cylinder 29 by rotation of handle 33. Afiixed to plate 30 by suitable means such as welding is a counter weight 34 which has sufficient weight such that when plug 3 is withdrawn from orifice 2 while mounted in hook members 22, the counterweight 34 will cause plug 3 to be maintained against the upper surface 12 of fiow channel 11. Thus with counterweight 34 maintaining the plug 3 against the upper surface 12 of flow channel 11 the upper surface 12 acts as a guide whereby when the plug is moved towards the orifice 2, said upper surface 12 guides the plug into the orifice 2. Further, maintaining plug 3 against upper surface 12 where upper surface 12 has an upward pitch away from orifice 2 forces the metal leaving orifice 2 to fiow under plug 3 thereby minimizing turbulence and regassing of the molten metal.

While the tapping block 1 and the plug 3 are shown in FIGURE 1 as being of one-piece construction, it is within the scope of this invention to fabricate plug 3, of a plurality of segments 3' and 3" as shown in FIGURE 6. With this construction it is preferable to separate segments and 3" from each other by suitable resilient refractory material 36 such as an aluminum silicate material, as previously described. Plug 3 and segments 3' and 3" may be mounted on a modified control rod 15', as shown in FIGURE 6. Control rod 15 is provided with a hollow center 78 adapted to permit passage of a tie rod 79. One end of tie rod 79 is provided with an opening 80 whereby end segment 3 of plug 3 may be afiixed by means of a pin 81 of suitable material such as stainless steel material such as steel.

'7 U passing through an opening 82 in segment 3" and opening 80 in tie rod 79. In order to maintain pin 81 in position external threads 83 may be provided on pin 81 which are adapted to engage internal threads 84 in opening 80. Thus pin 81 may be threaded into and through opening 80 to the position shown in FIGURE 6, the engagement of threads 83 and 84 maintaining pin 81 in position. Pin 81 may be provided with a slot or socket (not shown) whereby a suitable tool such as a screw driver or socket wrench can be employed for threading pin 81 into opening 80. Opening 82 may be plugged at either end with a mortar 98 of a material similiar to that of plug 3, to avoid contact between molten metal leaving orifice 2 with pin 81.

The segments 3 of plug 3 are all provided with axial openings 35 which have a diameter slightly larger than the diameter of tie rod 79 and are mounted thereon as shown in FIGURE 6. A suitable sleeve 16' affixed to a collar 17' by suitable means such as welding is provided over the end of plug 3 opposite the end portion 13. Collar 17' in turn is suitably affixed as by welding to control rod 15. As in the embodiment shown in FIG- URE l, a suitable resilient refractory material such as an aluminum silicate material, is provided between the segment 3' and the collar 17'. The segments 3' and 3" are maintained in compression by means of a suitable spring 86 provided at the end of tie rod 79 opposite the end provided with opening 80. This end of tie rod 79 extends beyond the end of control rod 15 and handle 33 a sufficient distance to allow for spring 86. Suitable washers 87 provided with extensions 88 of a diameter slightly smaller than the inside diameter of spring 86 are provided at each end of spring 86 and have central openings 89 adapted to fit over tie rod 79. Tie rod 79 is provided with suitable threads 95 on the end opposite the end having opening 80 which threads are adapted to engage the internal threads of nuts 90 and 91. Spring 86 and washers 87 are placed over the end of tie rod 79. Nuts 90 and 91 are threaded onto the end of tie rod 79 up against one of the washers 87 and moved in a direction to compress spring 86 whereby control rod 15 is urged toward plug 3 and tie rod 79 is urged away from plug 3. This compresses segments 3' between resilient refractory material 21' and segment 3" since the action of spring 86 tends to move plug segment 3" to the right and collar 17' and resilient refractory material 21 to the left.

While tapping block 1 is indicated as one-piece construction it may be fabricated from a plurality of sections for example, two sections 1 and 1" as shown in FIGURE 2. In such an instance generally the sections would be separated by a suitable resilient refractory material 37, such as an aluminum silicate material as described above. Segments 1' and 1" are held together by means of suitable clamps 9'2. Clamps 92 comprise bars 93 which are affixed to shell 27 of holding receptacle by means of bolts 94 which can be threaded into openings (not shown) in shell 27 of holding receptacle 5 having internal threads which can be engaged by external threads (not shown) on bolts 94. With a tapping block fabricated as shown in FIGURE 3, section 1' may be easily removed from 1" whereby the tap hole insert 8 may be easily removed without dismantling the wall of receptacle 5.

With the actuating means shown in FIGURES l and 3, valve plug 3 may be positioned relative to orifice 2 by either turning handle 33 or by rotation of shaft 23, to which book members 22 are afiixed. The actuating mechanism of this invention is well adapted to automatic control through the actuation of shaft 23 by automatic control means. Such automatic control means may be either electrical or pneumatic and may be a type whereby plug 3 automatically closes orifice 2 in the event of failure of the automatic control device.

One form of automatic control means is illustrated in FIGURES 4, 5 and 6. With reference at this time more particularly to FIGURES 4 and 5, it will be seen that shaft 23 is supported within bearings 97 mounted on support members 24 and connected to a second shaft 38 through universal joints 39 and 40 and a coupling shaft 41. Shaft 38 is supported within bearings 42 mounted on support members 43. Support members 43 are in turn suitably affixed to the shell 27 of holding receptacle 5. A crank arm 44 is suitably afiixed to shaft 38. Crank arm 44 may be moved upward or downward by a suitable control motor 45 through linkage means 46, employing a turn buckle adjustment means 47. Linkage means 46 is pivotally attached at one end to crank arm 44 and pivotally attached at its other end to a plate 48 which in turn is adjustably affixed to a crank arm 49 by means of bolts 50 and 51. Bolt 51 passes through a slot 52 in plate 48 and is threaded into the end of crank arm 49. Bolt 50 passes through an opening in plate 48 of substantially the same diameter as bolt 50. Thus the radial position of plate 48 may be adjusted relative to the radial position of crank 49 by loosening the bolts 50 and 51 and moving plate 48 to any new position permitted by slot 52 and retightening bolts 50 and 51.

Control motor 45 is a suitable conventional electrically operated valve control motor. One example of such a valve control motor is the Minneapolis-Honeywell Modutrol Motor M 904E. In a preferred embodiment of this invention a Modutrol Motor M 904E employing 15 second timing was used.

With reference more particularly to FIGURE 6, it will be seen that the control motor 45 is electrically connected to a suitable power source such as 110 volt alternating current supply by means of conductors 56 and 57 through a suitable transformer 58, fuse box 59 and a double pole single throw switch 60. The position of the crank arm 49 of motor 45 is controlled by a pressure actuated control device 61 through conventional electrical connections by means of conductors 62, 63 and 64. One example of a suitable pressure actuated control device 61 is the Minneapolis-Honeywell Pressuretrol Model L91A1X2. Pressure actuated control device 61 is in turn actuated by the molten metal level at a convenient location on the outlet side of orifice 2. Since in most conventional molten metal transfer systems a trough is employed, the molten metal level in such a trough may be used for purposes of control. If the molten metal is discharged directly into a casting mold the level in said casting mold may be employed for such control. The operation of this pressure actuated control device is effected by passing a suitable gas such as nitrogen which is inert to the molten metal through a tube 65, immersed in the molten metal. For purposes of description, it will be presumed that the tube 65 is immersed in the molten metal in a transfer trough 66. As shown in FIGURE 6, the nitrogen gas passes from a conventional gas cylinder 67 through a flow control valve 68 which insures a constant rate of flow of nitrogen through the system, the gas passing from the cylinder 67 to the valve 68 through a suitable conduit 69. From the valve 68 the gas passes through a conduit 70 to a suitable metering device 71 such as a Fisher and Porter rota meter 132G which indicates the rate of flow of gas. From the metering device 71 the gas passes through a suitable conduit 72 to a T 73 and then through a conduit 74 to tube 65. Also connected to T 73 is a conduit 75 connected to pressure actuated control device 61.

The operation of this system is as follows: As the molten metal level rises in trough 66 (or the casting mold as the case may be) the nitrogen pressure in conduits 72, 74 and 75 increases thus actuating the pressure actuated control device 61. The pressure actuated control device 61 then actuates the control motor 45 whereby plate 48 is rotated causing crank arm 44 to be moved downward. This rotates shafts 38, 41 and 23 in a counterclockwise direction thus moving the lower portion of book memhers 22 toward orifice 2. This in turn moves cylinder 29, control rod 15 and plug 3 toward orifice 2 thus restrioting the flow of metal between plug 3 and orifice 2. With the flow of metal restricted the level of molten metal in trough 66 will drop. As the molten metal level drops the pressure in conduit 75 is decreased whereby pressure actuated control device 61 is actuated. Control device 61 in turn actuates control motor 45 to raise crank arm 44 thereby rotating shafts 38 and 23 in a counterclockwise direction, thus moving the lower portion of hooks 22 away from orifice 2. This in turn moves shaft 28, control rod 15 and plug 3 away from orifice 2 permitting more metal to fiow through orifice 2. Through such action the system reaches equilibrium whereby the molten metal level in the trough 66, mold or other receiver is maintained constant.

An example of the invention, involving apparatus as shown in FIGURES 1, 4, 5 and 6 and applied to an aluminum melting and holding furnace, pertains to the casting of three 20 inch diameter 7075 aluminum alloy round ingots having a length on the order of 100 inches. Approximately 10,000 pounds of 7075 aluminum alloy were charged and melted in an oil fired open hearth furnace. The molten metal was stirred for about 5 minutes and sampled by spectographic analysis. Upon receipt of the analysis, the alloy composition was corrected to the exact 7075 alloy composition desired by adding the necessary alloying constituents. The composition of the melt was approximately 0.14% silicon, 0.22% iron, 1.89% copper, 2.58% magnesium, 0.24% chromium, 5.69% zinc, 0.03% titanium, balance aluminum. The molten metal was fluxed by a suitable method and means. The temperature of the metal was on the order of 1330" F.

The molten metal was level poured from the furnace through an orifice and a flow channel on the outlet side of said orifice embodying the principles of this invention into a transfer trough containing one outlet and into the casting mold. The orifice 2 had a configuration as shown in FIGURE 1 with a minimum diameter of 1% inches and a length of 2% inches. The radius of curvature of the inlet edge 6 was inch and the radius of curvature of the outlet edge 7 was A; inch with an arc length of 45. The orifice was inclined whereby the center line was at an angle to the horizontal of 20, with the outlet end at a higher position than the inlet end. The upper surface 12 of the flow channel 11 was hemicylindrical and had an upward pitch away from the orifice with the center line of said upper surface parallel to the center line of said orifice. The lower surface of the flow channel had a downward pitch away from the orifice of to the horizontal. The end portion 13 of plug 3 had the form of a frustrum of a cone with a rounded end portion while the spherical segment seating surface 14 had a radius of curvature of 1% inches. The body of the tapping block 1 was fabricated from phosphate bonded 90% alumina while the orifice insert 8 was fabricated from silicon nitride. The plug 3 was fabricated from silicon-nitride bonded silicon carbide.

The three aluminum alloy ingots were cast successively in the casting apparatus. This necessitated stopping the flow of molten metal when the casting of each ingot was completed in order to remove the ingot and prepare to cast the next ingot. Thus it was necessary to release and stop the flow of molten metal three times during the casting of the three ingots. With the apparatus of this invention, releasing and stopping the flow of molten metal was accomplished with ease and a minimum expenditure of labor. Further during the casting operation, the molten metal flow was easily controlled through the use of this apparatus. The 7075 aluminum alloy ingots pro duced had excellent metallurgical quality and were satisfactory for the production of high quality products by rolling, forging or extrusion operations. The ingots were subiectcd to reflectoscope tests and evidence of inclusions or porosity was found to be within the maximum limits set by sonic standards for 7075 plate.

As used herein the term aluminum is meant to cover high purity aluminum, commercial purity aluminum and aluminum alloys.

It is to be understood that various changes and modifications may be made in the foregoing apparatus and method and substitution of equivalent mechanism effected without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice for the passage of said molten metal and a plug adapted to be disposed at least partially within said orifice, said orifice having a rounded outlet edge, said plug having a spherical segment seating surface whereby a line of contact is made between said spherical segment seating surface and the outlet edge of said orifice, said plug also being provided with an elongated end portion extending from said spherical segment seating surface into said orifice and adapted to control the flow of molten metal passing through said orifice.

2. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice having a rounded inlet edge, a rounded outlet edge, and a flow channel at the outlet edge of said orifice having a downward pitch away from said orifice, a plug adapted to be disposed at least partially within said orifice characterized by a spherical segment seating surface whereby a line of contact is made between said spherical segment seating surface and the outlet edge of said orifice, said plug also being provided with an elongated end portion extending from said spherical segment seating surface into said orifice and adapted to control the flow of molten metal passing through said orifice.

3. The apparatus of claim 2 wherein said plug is formed from a plurality of segments and a resilient refractory material is provided between said segments.

4. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice having a rounded inlet edge, a rounded outlet edge, and a flow channel at the outlet edge of said orifice having a downward pitch away from said orifice, a plug adapted to be disposed at least partially within said orifice and characterized by a spherical segment seating surface whereby a line of contact is made between said spherical segment seating surface and the outlet edge of said orifice, said plug also being provided with an elongated end portion extending from said spherical segment seating surface and adapted to extend into said orifice to control the flow of molten metal passing through said orifice and means for moving said plug into and out of said orifice and for maintaining said plug in tight contact with said orifice.

5. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice and a flow channel on the outlet side of said orifice, said orifice having a rounded inlet edge, a rounded outlet edge, and being inclined at an angle to the horizontal with the outlet end at a higher position than the inlet end, the lower surface of said flow channel having a downward pitch away from said orifice, the upper surface of said flow channel having an upward pitch away from said orifice, said upper surface having a curvature such that a transverse crosssection thereof defines a segment of a circle, the center line of said curvature and the center line of said orifice being parallel, a plug adapted to be disposed at least partially within said orifice and having a configuration characterized by a 1 1 spherical segment seating surface whereby a line of contact is made between said spherical segment seating surface and the outlet edge of said orifice, and an elongated end portion adapted to extend from said spherical segment surface into said orifice to control the rate of flow of molten metal passing therethrough.

6. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice and a flow channel at the outlet of said orifice, said orifice having a rounded inlet edge and a rounded outlet edge, the minimum diameter of said orifice ranging from /4 to 4%. inches, the ratio of the radius of curvature of the inlet edge of said orifice to the diameter of said orifice ranging from 0.25 to 1.0, said orifice being inclined whereby the center line is at an angle to the horizontal ranging from to 60 with the outlet end at a higher position than the inlet end, the lower surface of said flow channel having a downward pitch of from 10 to 30 relative to the horizontal, the upper surface of said flow channel having an upward pitch away from said orifice, said upper surface having a curvature such that a transverse cross section defines a segment of a circle, the center line of said curvature and the center line of said orifice being parallel, a plug adapted to be disposed at least partially within said orifice and characterized by a spherical segment seating surface having a radius ranging from 0.6 to 1.2 times the exit diameter of said orifice whereby a line of contact is made between said spherical segment seating surface and said orifice, said plug having an elongated end portion extending from said spherical segment seating surface and into said orifice and adapted to control the flow of the molten metal passing through said orifice.

7. An apparatus for releasing, controlling and stopping the fiow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice and a flow channel on the outlet side of said orifice, said orifice having a rounded inlet edge and being inclined at an angle to the horizontal with the outlet end at a higher position than the inlet end, the lower surface of said flow channel having a downward pitch away from said orifice, the upper surface of said flow channel having an upward pitch away from said orifice, said upper surface having a curvature such that a transverse cross-section thereof defines a segment of a circle, the center line of said curvature and the center, line of said orifice being parallel, a plug adapted to be disposed at least partially within said orifice and having a configuration characterized by a spherical segment seating surface whereby a line of contact may be made between said spherical segment seating surface and the outlet edge of said orifice, and an elongated end portion adapted to extend from said spherical segment surface into said orifice to control the rate of flow of molten metal passing therethrough, means for moving said plug into and out of said orifice during discharge of molten metal to automatically control the flow of said molten metal issuing from said orifice comprising an externally threaded control rod on one end of which said plug is mounted, a pivotally mounted internally threaded supporting member adapted to engage the threads of said control rod, said supporting member being provided with a counterweight means whereby the end of said plug when withdrawn from said orifice is maintained against the upper surface of said flow channel, said control rod being provided with a handle on the end opposite the end affixed to said plug whereby said control rod and said plug may be moved longitudinally by rotation of said handle, a pair of hook members wherein said supporting member is pivotally mounted, said hook members being affixed to a shaft member whereby rotation of said shaft member causes the ends of said hook members within which said supporting member is supported to move toward or away from said orifice thus moving said control rod and said plug toward or away from said orifice, a pressure actuated control device, linkage means between said shaft member and said control device, said pressure actuated control device being connected to a gas conduit which discharges gas from a source under pressure into the molten metal issuing from said flow channel whereby raising of the level of said molten metal increases pressure in said conduit causing said control device to actuate said motor to move said control rod and plug toward said orifice while lowering of the molten metal level decreases the pressure whereby said control device actuates said motor to move said control rod and plug away from said orifice.

8. An apparatus for releasing, controlling and stopping the flow of molten metal from a molten metal holding receptacle comprising in combination a tapping block provided with an orifice and a flow channel on the outlet side of said orifice, said orifice having a rounded inlet edge, a rounded outlet edge, and being inclined at an angle to the horizontal with the outlet end at a higher position than the inlet end, the lower surface of said flow channel having a downward pitch away from said orifice, the upper surface of said fiow channel having an upward pitch away from said orifice, said upper surface having a curvature such that a transverse cross-section thereof defines a segment of a circle, the center line of said curvature and the center line of said orifice being parallel, a plug adapted to be disposed at least partially within said orifice and having a configuration characterized by a spherical segment seating surface whereby a line of contact is made between said spherical segment seating surface and the outlet edge of said orifice, and an elongated end portion adapted to extend from said spherical segment surface into said orifice to control the rate of flow of molten metal passing therethrough, means for moving said plug into and out of said orifice comprising an externally threaded control rod on one end of which said plug is mounted, a pivotally mounted internally threaded supporting member adapted to engage the threads of said control rod, said supporting member being provided with counterweight means whereby the end of said plug when withdrawn from said orifice is maintained against the upper surface of said flow channel, said control rod being provided with a handle on the end opposite the end affixed to said plug whereby said control rod and said plug may be moved longitudinally by rotation of said handle.

9. The apparatus of claim 8 including means for positioning said plug relative to said orifice during discharge of molten metal to automatically control the flow of said molten metal issuing from said orifice.

References Cited in the file of this patent UNITED STATES PATENTS 706,841 Meehan Aug. 12, 1902 771,675 Smith Oct. 4, 1904 1,097,345 Meyer May 19, 1914 1,102,236 Brennan July 7, 1914 1,277,899 Freeman Sept. 3, 1918 1,401,072 Haarmann Dec. 20, 1921 1,519,290 Baurichter Dec. 16, 1924 1,944,611 Reinartz et a1 Ian. 23, 1934 2,024,132 Sander Dec. 10, 1935 2,557,834 McMullen June 19, 1951 2,609,318 Swentzel Sept. 2, 1952 2,702,425 Thompson Feb. 22, 1955 2,736,935 Shea Mar. 6, 1956 2,821,378 Tama Jan. 28, 1958 2,921,351 Momm Jan. 19, 1960 FOREIGN PATENTS 745,037 Great Britain Feb. 15, 1956 548,297 Belgium June 15, 1956 

5. AN APPARATUS FOR RELEASING, CONTROLLING AND STOPPING THE FLOW OF MOLTEN METAL FROM A MOLTEN METAL HOLDING RECEPTACLE COMPRISING IN COMBINATION A TAPPING BLOCK PROVIDED WITH AN ORIFICE AND A FLOW CHANNEL ON THE OUTLET SIDE OF SAID ORIFICE, SAID ORIFICE HAVING A ROUNDED INLET EDGE, A ROUNDED OUTLET EDGE, AND BEING INCLINED AT AN ANGLE TO THE HORIZONTAL WITH THE OUTLET END AT A HIGHER POSITION THAN THE INLET END, THE LOWER SURFACE OF SAID FLOW CHANNEL HAVING A DOWNWARD PITCH AWAY FROM SAID ORIFICE, THE UPPER SURFACE OF SAID FLOW CHANNEL HAVING AN UPWARD PITCH AWAY FROM SAID ORIFICE, SAID UPPER SURFACE HAVING A CURVATURE SUCH THAT A TRANSVERSE CROSS-SECTION THEREOF 